Process for preparation of pastable polymers

Abstract

The present invention relates to a single-stage batch process for preparation of pastable polymers, in particular of vinyl chloride homo- and copolymers, by the microsuspension process, where these in a blend with plasticizers give PVC pastes, also termed plastisols, with very low viscosities and with very low emulsifier contents.

1 . A process for preparation of pastable polymers composed of ethylenically unsaturated monomers by means of batch polymerization or copolymerization in a microsuspension process with use of dispersing equipment using the rotor-stator principle or (any) other homogenizing machine(s), where a bimodal primary particle size distribution of the polymer dispersion is generated via a single-stage process optimized with respect to dispersing pressure and shear gap width of the disperser system. 
   
   
       2 . The process as claimed in  claim 1 , where the pastable polymer is a polymer of vinyl chloride or of a mixture of vinyl chloride with up to 30 percent by weight of copolymerizable monomers. 
   
   
       3 . The process as claimed in  claim 1 , wherein the diameter of the primary particles is in the range from 0.05-1.0 μm for the population P1 and is in the range from 1.5-20 μm for the population P2. 
   
   
       4 . The process as claimed in  claim 1 , wherein the ratio by volume of the particle populations P1 and P2 of the bimodal distribution is from 90:10 to 10:90, preferably in the range from 60:40 to 40:60. 
   
   
       5 . The process as claimed in  claim 1 , wherein the amounts of emulsifier/coemulsifier used to stabilize the polymer dispersion are in each case from 0.3-2.0% by weight. 
   
   
       6 . The process as claimed in  claim 1 , wherein mixtures having low content of emulsifier/coemulsifier are polymerized with amounts of emulsifier/coemulsifier which are in each case preferably from 0.4-0.8% by weight. 
   
   
       7 . The process as claimed in  claim 1 , wherein only from 30-80% of the amount of monomer is transferred by way of the dispersing equipment into the polymerization reactor, and the remaining proportion is fed directly into the polymerization tank. 
   
   
       8 . A pastable polymer, prepared by the process as claimed in  claim 1 . 
   
   
       9 . A product, produced from a polymer as claimed in  claim 8 .